Processes of separating nitrilehydrocarbon mixtures



, ofwi'th hydrocarbons and it,com'prises processes from the extractphase.

Patented Oct. 11, 1938,

[ .uirao STAT ESfP-ATEN P rnocassss orssrm'rnvc marm- HYDIIDOABBOAnderson w. wmimo. Pool, can cago, ni asaig'nors to Armour and Company,Chicago, 111., a corporation of Illinois m nst ous-i5,- x

This invention relates to processes of separating aliphatic nitrilesfrom admixtures therewherein such mixtures are treated with apreferential solvent material for the nitriles to form an extract phasecontaining the nitrile dissolved in the solvent and a hydrocarbon phase,the'two phases separated and thenitrile then separated Recentlyprocesses have been described, as in U. S. Patents 1,991,955. 2,033,536and. 2933537, for preparing nitriles of relatively low molecular weightfrom "*nitriles of high molecular-weight.

For example, by methods of pyrolysis higher ali-' phatic 'nitriles suchas stearo and palmitonitrile mixtures of nitrilesKand hydrocarbonscan.be"

can be "cracked" to give reaction products con- 1 taining nitrileshaving four, live,- six and seven carbon atoms. The cracking operation'can be so controlled that nitriles of almost any desired number ofcarbon atoms say from six to eleven can be prepared from nitriles ofhigher molecular weight. In these processesthe reaction prod-.

And the pure nitriles are starting ma.--

ing from six to about eleven carbon atoms;

Hitherto reactive compounds of. this nature have *not been availableon acommercialscaleand at a price which-would enable them tobe used .ingreat quantities. In other words, the de-' velopment of processes ofpreparing nitriles. from -the cheap fatty acid sources has made itpossible for us to supply largequantities of aliphatic compounds havingfrom about five to ten carbon atoms in the allryl group togetherwith ahighly reactive polar, or CN' group. This means that many aliphaticamines, alcohols and acids.

' of from six to ten carbon atoms can be prepared p at lowcost. Hithertothese materials have been so expensive that they could not be used inthe artS. I V A ,1 I, its stated. mixtures of nitrilesfalone can-beseparated readily by fractional distillation. It

.is difflcult however to separate mixtures-of'the nitriles andhydrocarbons in this manner. Constant boiling mixtures are obtained inmanyinstances and there are other objections. The most productive sourceof the lower nitriles is-the higher fatty acid nitriles because of theease with which thesecanbe crackedto give the desired lower nitriles.But, asstated, the cracked products contain quantities of hydrocarbons.

Consequently we have set ourselves. to the "problem of discoveringmethods by which these separated to obtain the nitriles which can' thenbe fractionally distilled if desired. And we have discovered thatmixtures of this type can be treatedwith preferential solvents in such amanner that the nitriles are dissolved to the exclusion of thehydrocarbons. -From the extract phase of nitriles and solvent we canthen recover the nitriles andrecover the solvent for re-use. Manyexperiments have been necessary however since what will or will. not actas a. preferential solvent for such mixtures could notv be determined inadvance of experiment. Many solvents which might seemingly dissolve thenitriles with 'out' affecting the hydrocarbons actually form homogeneousmixtures without leading to the formation of stratified layersofhydrocarbon and nitrile Because of the pronounced mu.-

tual solubility of the nitriles and aliphatic hy- 'drocarbonamanysolvents dissolve the nitrile but the nitrile acts as a mutual secondsolvent for both hydrocarbon and added solvent; This leads to mutualsolution of all constituents. Consequently the search for satisfactorypreferential solvents 'has been a diihcult task and'many un expecteddiscoveries have been made; 7 V For example, we have discovered thatwatery solutions of aliphatic alcohols canbe used suecess'iully providedcare is taken to control the quantity of water present. Thus a '75percent, I

solution of methyl alcohol will dissolve the nitrile but not thealiphatic hydrocarbons present but percent methyl alcoholforms ahomogeneous solution of alcohol, water, nitriles, and hydrocarbons.Hence the application of the broad, old, 'idea of preferentialextraction with a suitable solvent to. mixtures of the type with which=we-are concerned has notlbeen asimple matter.

Moreover having discovered a suitable prefernentialsolvent which willgive an extract containing nitriles dissolved in the solvent, the nextstep is the liberation of the dissolved nitrile from ",thextract. Hereagain many solvents, apparentlysuitable .as preferential solvents mustbe d scardedbecauseof the difficulties in separatin'g the nitriletherefrom. What we have sought is solvents which would dissolve thenitriles but not 3 claimed the use of amines for separating nitriles.

and hydrocarbons; and in our application, Serial No. 169,328, we havemore particularly h v 2,138,007 preferential solvents. Among them may bementioned aniline, ethyl amine, isopropyl amine, normal propyl amine,diethyl amine, allyl amine, v

true-hydrocarbon mixture is one composed of the products of crackingrelatively high molecular benzyl amine, secondary butyl amine, isobutylamine, normal butyl airline, isoallyl-amine, normal amyl amine, dinormalpropyl amine, pyridine, diallyl amine and cyclohexyl amine. For example100 parts by volume of the nitrile-hydrocarbon mixture is mixed with 100parts .by volume of aniline and the-mixture cooled to C.

This gives an upper layer consisting of to parts of hydrocarbonscontaining 0.5 percent nitrogen and a lower layer composed of 160 partsby volume containing aniline and nitriles.. To this lower layer we adddilute hydrochloric. acid solu-, tion until the nitriles separate out.This gives us 60 parts of a nitrile fraction containing percent ofnitrogen. The aniline can be recovered for reuse by treating thesolution of aniline hynitriles dissolved in the preferential solvent 'asthe extract phase.

In, our co-pending application, Serial No. 169,-

2'72, we have more particularly claimed the use of carboxylic acids forseparating nitriles and hydrocarbons; in our co-pending application,Serial No. 169,273, we have more particularly the use of phenolsioriseparating nitriles and hydrocarbons. I

Having thus described our invention what; we

claim is: i l

1. The process oi! separating aliphatic hitriles 60% and less than.85%to dissolve thenitriles but not dissolve substantial amounts of thehydrocarbons, separating the extract phase from the hydrocarbon phase,adding water to 'the ex- I tract phase to liberate the nitriles therein.as a layer, and separating the nitrile layer from the aqueous alcoholiclayer.

2. The process as in claim 1 wherein hol is methyl alcohol.

aqueous alcohol solution comprises an aqueous methyl .alcohol solution.

3. The process as in claim 1 wherein the niweight fatty acid nitriles.

. 4. The process as in claim 1 wherein the aqueis one composed oi theproducts of cracking relatively high molecularweight fatty acidnitriles.

5. The processor separating aliphatic nitriles from mixtures thereofwith aliphatic hydrocarbons which comprisesextracting thenitrile-hydrocarbon mixture with I an aqueous aliphatic alcohol solutionor about 75 percent strength,

separating an extract composed of nitriles and the alcoholic solutionfrom the hydrocarbon layer, extracting the hydrocarbon layer with anaqueous alcohol having about 80 percent strength separating thehydrocarbon layer from the extract. layer, extracting the hydrocarbonlayer with an aqueous alcohol of. about 85 percent strength, separatingthe hydrocarbon layer from the extract layer, and recovering nitrilesfrom" J said alcoholic extract layers by adding water .thereto.

6. The process asin clalm 5 wherein the 7. The process as in claim 5wherein the lar weightiatty-acid nitriles.

-' 8. The process as inclaim 5 wherein the alcohol is methyl alcohol andthe nitrlle hydrocarn mixture is one'composed oi! the products or acidnitriles. p

9. In the process of separating aliphatic nitrlles mixtures thereof withaliphatic hydrocarbons; the 'step comprising extracting the mixture withan aqueous aliphatic alcohol solu-'- tion which will dissolve thenitriles but notdissolve substantial amounts of the hydrocarbons.

.10. The processas in claim 9 wherein the alcohol is-methyl alcohol.

' wnnsuo. roon alconitrile-hydrocarbon mixture is one composed of. theproducts oi! cracking relatively high molecu NW.RAIBTON.

